On-site calibration method for terminal device of variable air volume air conditioning system

Abstract

The present invention discloses a field calibration method for a terminal device of a variable air volume air conditioning system, which relates to the technical field of variable air volume air conditioning. The method includes the following steps: S1. Install a cross-shaped Pitot tube on the pipeline and connect it to the terminal controller respectively; S2. Read the measured pressure difference of the terminal controller through the communication protocol; at the same time, measure the pressure difference at the Pitot tube with a handheld pressure difference meter; S3. Under at least two working conditions, read the pressure difference measured by the handheld pressure difference meter and the measured pressure difference of the terminal controller respectively, and finally calculate the pressure difference coefficient k and the pressure difference deviation C through the formula:; S4. Set the calculated pressure difference coefficient k and pressure difference deviation C into the terminal controller. Through the handheld pressure difference meter, the present invention can perform relatively accurate calibration of the variable air volume terminal device on the project site, simplifies the calibration process, eliminates the need for complex laboratory equipment, and significantly improves the efficiency of on-site construction.

Description

Technical Field

[0001] The present invention relates to the technical field of variable air volume air conditioning, and specifically provides a field calibration method for the terminal device of a variable air volume air conditioning system. Background Art

[0002] A variable air volume system is an all-air air conditioning system that adjusts the indoor temperature by changing the volume of air supplied into the room, and its supply air state remains unchanged. The variable air volume air conditioning system consists of an air handling unit, a supply air system, a terminal device, an automatic control device, etc. Among them, the terminal device and the automatic control device are key equipment of the variable air volume system. They can receive the instructions of the room temperature regulator and automatically adjust the supply air volume according to the room temperature to meet the indoor load requirements.

[0003] In a variable air volume air conditioning system, the terminal controller measures the real-time air volume, compares it with the required air volume, and then adjusts the valve opening to control the air volume. Therefore, the measurement accuracy of the real-time air volume is very important for the operation of the system. Usually, after determining the brand and model of the variable air volume terminal air box and the terminal controller, the terminal controller needs to be installed on the variable air volume terminal air box before the overall installation to calibrate the measured air volume, and the entire calibration process is usually carried out in the factory of the variable air volume terminal air box manufacturer, and a calibration table is required.

[0004] After retrieval, Chinese Patent (Publication No.: CN104566775B) discloses a variable air volume air conditioning system and a control method, which includes the following steps: calculating the required air volume value of the variable air volume terminal according to the preset temperature parameter and the actual temperature parameter; at the same time, detecting the air leakage value of the variable air volume air conditioning system; adjusting the speed of the fan in the variable air volume air conditioning system according to the air leakage value, the required air volume value and the maximum speed of the fan in the variable air volume air conditioning system, so that the supply air volume of the variable air volume terminal in the variable air volume air conditioning system is equal to the required air volume of the variable air volume terminal in the variable air volume air conditioning system.

[0005] If the terminal controller of a variable air volume air conditioner is replaced, it is necessary to re-calibrate the measured air volume. However, due to the large volume of the variable air volume terminal air box and the inconvenience of transportation back and forth, a relatively accurate on-site calibration method is very necessary. Therefore, the present invention proposes an on-site calibration method for the terminal device of a variable air volume air conditioning system. Summary of the Invention

[0006] The purpose of the present invention is to provide an on-site calibration method for the terminal device of a variable air volume air conditioning system to solve the problems mentioned in the above background art.

[0007] The present invention can be realized by the following technical solutions: An on-site calibration method for the terminal device of a variable air volume air conditioning system, the method includes the following steps:

[0008] S1. Install a cross-shaped Pitot tube on the pipeline to lead out two measurement ports, namely the high and low ports, corresponding to the total pressure and static pressure respectively, and connect the high and low measurement ports to the high and low differential pressure interfaces on the terminal controller respectively;

[0009] S2. Read the measured differential pressure of the terminal controller through the communication protocol ;

[0010] Meanwhile, measure the differential pressure at the Pitot tube with a handheld differential pressure gauge ;

[0011] S3. Calculate the air volume through the formula and ;

[0012] where S is the cross-sectional area of the air duct, is the air density, is the measured differential pressure of the terminal controller, and k is the differential pressure coefficient;

[0013] Therefore, under at least two working conditions, read the differential pressure measured by the handheld differential pressure gauge and the measured differential pressure of the terminal controller , and finally through the formula: , calculate the differential pressure coefficient k and the differential pressure deviation C;

[0014] S4. Set the calculated differential pressure coefficient k and differential pressure deviation C into the terminal controller to complete the calibration.

[0015] A further technical improvement of the present invention is that in step S2, time series monitoring is performed on the differential pressure measured by the handheld differential pressure gauge, and after its fluctuation stability, the average differential pressure within a preset time is taken as the differential pressure measured by the handheld differential pressure gauge , and its steps include:

[0016] A1. Continuously record the differential pressure data by measuring with the handheld differential pressure gauge , and determine the recording time interval and the total monitoring duration T;

[0017] A2. Perform time series monitoring on the differential pressure data ;

[0018] Starting from time , collect the differential pressure data at N consecutive time points , and record it as a time series: ;

[0019] A3. Calculate the fluctuation range and change rate of the time series, including:

[0020] Calculate the average value of the time series: Wherein, is the average value of the time series, is the differential pressure data measured by the hand-held differential pressure gauge at the i-th time point;

[0021] The formula for calculating the fluctuation range is: , wherein, R is the fluctuation range of the time series, is the maximum value of the differential pressure data in the time series, is the minimum value of the differential pressure data in the time series;

[0022] The change rate of the time series is calculated by calculating the standard deviation of the time series, and the formula is: ;

[0023] The preset allowable fluctuation range threshold and the preset standard deviation threshold ;

[0024] When the fluctuation range R of the time series ≤ the fluctuation range threshold , and the standard deviation of the time series ≤ the standard deviation threshold , it is determined that the differential pressure data measured by the hand-held differential pressure gauge meets the stability, and the differential pressure data at subsequent times is marked as the steady-state differential pressure, and the stable time point is recorded at the same time.

[0025] At a period of time after the stable time point , calculate the mean value of the steady-state differential pressure, and the formula is: , wherein, is the mean value of the steady-state differential pressure, Z is the number of sampling points corresponding to the time M, is the differential pressure data marked as the steady-state differential pressure.

[0026] A5. Repeat steps A1 - A4 to calculate the measured differential pressure marked as the steady-state differential pressure of the end controller;

[0027] A6. Apply the measured differential pressure marked as the steady-state differential pressure of the end controller and the differential pressure marked as the steady-state differential pressure of the hand-held differential pressure gauge to the calculation in step S3, that is:

[0028] The air volume calculation formula is: ;

[0029] The calculation formulas for the differential pressure coefficient k and the differential pressure deviation C are: .

[0030] A further technical improvement of the present invention lies in: under dynamic conditions, by adjusting the frequency and fluctuation of the air intake volume of the variable air volume air conditioner, and then monitoring the change frequency and fluctuation of the air volume at the handheld differential pressure gauge and the terminal controller to detect the air volume change delay, the steps include:

[0031] Z1. By adjusting the input frequency of the air intake volume of the variable air volume air conditioner , simulate periodic fluctuations;

[0032] And by setting multiple input frequencies , observe the responses of the variable air volume air conditioning system at different frequencies;

[0033] Z2. Real-time monitor the differential pressure change of the terminal device, including:

[0034] Collect the differential pressure time series through the handheld differential pressure gauge and record the differential pressure change at the measuring Pitot tube in the pipeline ;

[0035] Z3. Through the terminal controller, record the air volume ;

[0036] Z4. According to the changes in the air intake volume and differential pressure, calculate the delay time of the differential pressure change relative to the air intake volume change , ; where, is the phase difference of the air volume change relative to the air intake volume;

[0037] According to the changes in the air intake volume and air volume, calculate the delay time of the air volume change relative to the air intake volume change , ; where, is the phase difference of the air volume change relative to the air intake volume;

[0038] Finally, through the response delay from the air intake volume to the differential pressure and the response delay from the air intake volume to the air volume, obtain the system delay time, and the formula is .

[0039] A further technical improvement of the present invention lies in: plotting the system delay time at different input frequencies to obtain the frequency response curve;

[0040] By analyzing the system delay time of the variable air volume air conditioning system at different input frequencies , judge the frequency dependence of the response speed of the variable air volume air conditioning system.

[0041] A further technical improvement of the present invention lies in: the terminal controller establishes a dynamic correction model based on the system delay time: ;

[0042] Where, is the dynamic pressure difference coefficient, and k is the pressure difference coefficient calculated in step S4;

[0043] α is the delay correction coefficient, which is determined by experimental fitting and reflects the influence of system delay on k;

[0044] Under dynamic conditions, the air volume calculation formula is corrected as: ;

[0045] And if it is found that under dynamic conditions, if the pressure difference deviation C deviates from the calibrated value, then through the formula: for correction;

[0046] In the formula, is the dynamic pressure difference deviation, and β is the deviation correction coefficient, which is determined by experimental fitting;

[0047] By introducing the delay correction coefficients α and β, the calibration results can adapt to the changes in dynamic air volume and pressure difference, solve the problem that traditional calibration methods are only applicable to steady-state conditions, reduce the calibration error caused by the delay effect, and make the calibration results closer to the actual air volume.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] With the hand-held differential pressure gauge, the present invention can perform relatively accurate calibration of variable air volume terminal devices on-site, simplifies the calibration process, eliminates the need for complex laboratory equipment, significantly improves the efficiency of on-site construction, and uses the hand-held differential pressure gauge and on-site real-time data processing technology. The calibration process does not require high-precision experimental equipment and professional technical personnel to operate, reducing the technical difficulty of calibrating variable air volume terminal devices;

[0050] And by performing time series analysis on the differential pressure data collected by the hand-held differential pressure gauge, the technical solution can extract the average value of the differential pressure as the calibration basis after the fluctuation stabilizes, avoiding the influence of instantaneous fluctuations on the calibration accuracy. This makes the on-site calibration results closer to the actual operating conditions and ensures the calibration accuracy;

[0051] At the same time, the solution can cope with problems such as air volume fluctuations and unstable pressure differences that may exist in the on-site environment by introducing dynamic monitoring technology and steady-state differential pressure calculation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] For the convenience of those skilled in the art to understand, the present invention will be further described below with reference to the accompanying drawings.

[0053] Figure 1 is the method flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0054] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following specifically describes in detail the specific implementation manner, structure, features and their effects of the present invention in combination with the accompanying drawings and preferred embodiments. Embodiment 1

[0055] Please refer to Figure 1 As shown, the present invention provides a field calibration method for the terminal device of a variable air volume air conditioning system, and the method includes the following steps:

[0056] S1. Install a cross-shaped Pitot tube on the pipeline to lead out two high and low measurement ports, corresponding to the total pressure and static pressure respectively, and connect the two high and low measurement ports to the upper and lower differential pressure interfaces of the terminal controller respectively;

[0057] Measure the high and low differential pressure through the principle of total pressure - static pressure = dynamic pressure, that is, the dynamic pressure. Calculate the air velocity flowing through the pipeline through the dynamic pressure, and then measure the air volume in combination with the pipeline cross-sectional area;

[0058] S2. Read the measured differential pressure of the terminal controller through the communication protocol ;

[0059] At the same time, measure the differential pressure at the Pitot tube through a handheld differential pressure gauge ;

[0060] S3. Measure the air volume through the formula and ;

[0061] In the formula, S is the cross-sectional area of the air duct, is the air density, is the measured differential pressure of the terminal controller, and k is the differential pressure coefficient;

[0062] Therefore, under at least two working conditions, read the differential pressure measured by the handheld differential pressure gauge and the measured differential pressure of the terminal controller respectively. Finally, through the formula: , calculate the differential pressure coefficient k and the differential pressure deviation C;

[0063] S4. Set the calculated differential pressure coefficient k and differential pressure deviation C into the terminal controller to complete the calibration.

[0064] Specific case:

[0065] During operation, connect the Pitot tube on the BOX to the terminal controller and the handheld differential pressure gauge respectively through the Y-shaped interface to ensure correct + / - connection pipes;

[0066] Turn on the Bluetooth of the handheld differential pressure gauge. Install the testo smart APP on the mobile phone. Turn on the Bluetooth and connect the handheld differential pressure gauge through the APP. Set the pitot tube coefficient = 1, set the correction coefficient = 1, and set the area to the corresponding area of 40107 in the terminal controller;

[0067] In the APP, through Options - Application Scope - My Measurement Field - + Measurement Program - Differential Pressure ( ), enter the measurement. In the upper right corner, select Options - Point by Point;

[0068] Connect the terminal controller to the computer through the serial port. Open the XCVAVConfigTool, modify the connection parameters and then connect, and read the device parameters;

[0069] In the APP, click "Fully Open". When the damper opening reaches 100, there will be a reading for "Differential Pressure at Full Open of Damper". Wait for about 5 seconds (until the air flow is stable), click "Fully Open" again and at the same time click the "Accept" button on the mobile APP, and fill the number in the result column of the APP at this time into "Measured Differential Pressure at Full Open" in the XCVAVConfigTool;

[0070] Repeat the above operations in the "Half Open" state. Then, in the XCVAVConfigTool, there will be numbers for both the differential pressure between full open / half open of the damper and the measured differential pressure between full open / half open. At this time, click "Calculate Differential Pressure Parameters" to generate "Differential Pressure Coefficient K" and "Differential Pressure Offset";

[0071] Finally, click "Save Device Parameters" to successfully write to the device and the parameters will take effect. Embodiment 2

[0072] A on-site calibration method for the terminal device of a variable air volume air conditioning system, the method comprising the following steps:

[0073] S1. Install a cross-shaped pitot tube on the pipeline to lead out two high and low measurement ports, corresponding to the total pressure and static pressure respectively, and connect the two high and low measurement ports to the upper and lower differential pressure interfaces of the terminal controller respectively;

[0074] Measure the high and low differential pressure through the principle of total pressure - static pressure = dynamic pressure, which is the dynamic pressure. Calculate the air velocity flowing through the pipeline from the dynamic pressure, and then measure the air volume in combination with the pipeline cross-sectional area;

[0075] S2. Read the measured differential pressure of the terminal controller through the communication protocol ;

[0076] At the same time, measure the differential pressure at the pitot tube through a handheld differential pressure gauge ;

[0077] Perform time - series monitoring on the differential pressure measured by the handheld differential pressure gauge, and after its fluctuation stability, take the average differential pressure within a preset time as the differential pressure measured by the handheld differential pressure gauge , and its steps include:

[0078] A1. Continuously record differential pressure data by measuring with the handheld differential pressure gauge , and determine the recording time interval and the total monitoring duration T, that is time points;

[0079] A2. Conduct time - series monitoring on the differential pressure data ;

[0080] Starting from time , collect differential pressure data at N consecutive time points , and record it as a time series: ;

[0081] A3. Calculate the fluctuation range and change rate of the time series, including:

[0082] Calculate the average value of the time series: ;

[0083] In the formula, is the average value of the time series;

[0084] is the differential pressure data measured by the handheld differential pressure gauge at the i - th time point;

[0085] The formula for calculating the fluctuation range is: ;

[0086] In the formula, R is the fluctuation range of the time series;

[0087] is the maximum value of the differential pressure data in the time series, is the minimum value of the differential pressure data in the time series;

[0088] Calculate the change rate of the time series by calculating the standard deviation of the time series, and its formula is: ;

[0089] The preset allowable fluctuation range threshold and the preset standard deviation threshold ;

[0090] Compare the fluctuation range of the time series and the standard deviation of the time series with the corresponding fluctuation range threshold and the standard deviation threshold respectively;

[0091] When the fluctuation range R of the time series ≤ the fluctuation range threshold and the standard deviation of the time series ≤ the standard deviation threshold When it is determined that the differential pressure data measured by the handheld differential pressure gauge meets the stability, and the differential pressure data at subsequent times is marked as the steady-state differential pressure, and the stable time point is recorded ;

[0092] A4. At the stable time point For a period of time after that, calculate the mean value of the steady-state differential pressure. The formula is: wherein, is the mean value of the steady-state differential pressure, Z is the number of sampling points corresponding within time M, is the differential pressure data marked as the steady-state differential pressure;

[0093] A5. Repeat steps A1 - A4 to calculate the measured differential pressure of the end controller marked as the steady-state differential pressure ;

[0094] S3. Measure the air volume through the formula ;

[0095] wherein, S is the cross-sectional area of the air duct, is the air density, is the measured differential pressure of the end controller, and k is the differential pressure coefficient;

[0096] Therefore, under at least two working conditions, respectively read the differential pressure measured by the handheld differential pressure gauge and the measured differential pressure of the end controller , and finally calculate the differential pressure coefficient k and the differential pressure deviation C through the formula:

[0097] S4. Set the calculated differential pressure coefficient k and differential pressure deviation C into the end controller to complete the calibration. Embodiment 3

[0098] A field calibration method for the terminal device of a variable air volume air conditioning system, the method comprising the following steps:

[0099] S1. Install a cross-shaped Pitot tube on the pipeline to lead out two measurement ports, high and low, corresponding to the total pressure and static pressure respectively, and connect the high and low measurement ports to the high and low differential pressure interfaces on the end controller respectively;

[0100] S2. Read the measured differential pressure of the end controller through the communication protocol ;

[0101] At the same time, measure the differential pressure at the Pitot tube through a handheld differential pressure gauge ;

[0102] Perform time - series monitoring on the differential pressure measured by the handheld differential pressure gauge, and after its fluctuation stability, take the average differential pressure within a preset time as the differential pressure measured by the handheld differential pressure gauge , and its steps include:

[0103] A1. Continuously record differential pressure data by measuring with the handheld differential pressure gauge , and determine the recording time interval and the total monitoring duration T, that is time points;

[0104] A2. Perform time - series monitoring on the differential pressure data ;

[0105] Starting from time , collect differential pressure data at N consecutive time points , and record it as a time series: ;

[0106] A3. Calculate the fluctuation range and change rate of the time series, including:

[0107] Calculate the average value of the time series: ;

[0108] The formula for calculating the fluctuation range is: ;

[0109] Calculate the change rate of the time series by calculating the standard deviation of the time series, and its formula is: ;

[0110] The preset allowable fluctuation range threshold and the preset standard deviation threshold ;

[0111] Compare the fluctuation range of the time series and the standard deviation of the time series with the corresponding fluctuation range threshold and the standard deviation threshold respectively;

[0112] When the fluctuation range R of the time series ≤ the fluctuation range threshold , and the standard deviation of the time series ≤ the standard deviation threshold , it is determined that the differential pressure data measured by the handheld differential pressure gauge meets the stability, and mark the differential pressure data at subsequent times as the steady - state differential pressure, and record the stable time point ;

[0113] A4. At a period of time after the stable time point ​ Calculate the mean value of the steady-state pressure difference within the formula: ;

[0114] A5. Repeat steps A1 - A4 to calculate the measured pressure difference of the end controller marked as the steady-state pressure difference ;

[0115] S3. Through the formula Measure the air volume;

[0116] In the formula, S is the cross-sectional area of the air duct, is the air density, is the measured pressure difference of the end controller, and k is the pressure difference coefficient;

[0117] Therefore, under at least two working conditions, respectively read the pressure difference measured by the handheld pressure difference gauge and the measured pressure difference of the end controller , and finally through the formula: , calculate the pressure difference coefficient k and the pressure difference deviation C;

[0118] Under dynamic working conditions, by adjusting the frequency and fluctuation of the air volume input of the variable air volume air conditioner, and then monitoring through the change frequency and fluctuation of the air volume output of the handheld pressure difference gauge and the end controller, detect the air volume change delay, and its steps include:

[0119] Z1. By adjusting the air volume input frequency of the variable air volume air conditioner, simulate periodic fluctuations, and the formula is as follows: ;

[0120] In the formula, is the air volume at time t;

[0121] is the average air volume and is the reference value of the air volume fluctuation;

[0122] A is the amplitude of the air volume fluctuation, indicating the maximum change range of the air volume relative to the average air volume during the fluctuation process;

[0123] is the sine function, indicating the periodic change of the air volume fluctuation, and by multiplying it with A, the fluctuation range [-A, A] of the air volume is obtained;

[0124] And by setting multiple input frequencies , observe the response of the variable air volume air conditioner system at different frequencies;

[0125] Z2. Real-time monitor the pressure difference change of the end device, including:

[0126] Collect the pressure difference time series through the handheld pressure difference gauge and record the pressure difference change at the measuring pitot tube in the pipeline ;

[0127] Z3. Record the air volume through the end controller ;

[0128] Z4. Calculate the delay time of the differential pressure change relative to the air volume change according to the changes of the air volume and the differential pressure ;

[0129] ;

[0130] In the formula, is the phase difference of the air volume change relative to the air volume;

[0131] Calculate the delay time of the air volume change relative to the air volume change according to the changes of the air volume and the air volume ;

[0132] ;

[0133] In the formula, is the phase difference of the air volume change relative to the air volume;

[0134] Finally, obtain the system delay time through the response delay from the air volume to the differential pressure and the response delay from the air volume to the air volume, and the formula is .

[0135] Plot the system delay time at different input frequencies to obtain the frequency response curve;

[0136] By analyzing the system delay time of the variable air volume air conditioning system at different input frequencies judge the frequency dependence of the response speed of the variable air volume air conditioning system.

[0137] The end controller establishes a dynamic correction model based on the system delay time: ;

[0138] In the formula, is the dynamic differential pressure coefficient, k is the measured differential pressure marked as the steady-state differential pressure and the differential pressure marked as the steady-state differential pressure calculated;

[0139] α is the delay correction coefficient, which is determined by experimental fitting and reflects the influence of system delay on k;

[0140] Under dynamic conditions, the air volume calculation formula is corrected to: ;

[0141] And if it is found that under dynamic conditions, if the differential pressure deviation C deviates from the calibration value, then through the formula: Make corrections;

[0142] In the formula, is the dynamic pressure difference deviation, β is the deviation correction coefficient, which is determined by experimental fitting;

[0143] By introducing the delay correction coefficients α and β, the calibration result can adapt to the changes in dynamic air volume and pressure difference, solve the problem that the traditional calibration method is only applicable to steady-state working conditions, reduce the calibration error caused by the delay effect, and make the calibration result closer to the actual air volume.

[0144] S4. Set the calculated dynamic pressure difference coefficient and the dynamic pressure difference deviation into the end controller, and the dynamic calibration can be completed.

[0145] The above is only a preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to obtain an equivalent embodiment with equivalent changes within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A field calibration method for a terminal device of a variable air volume air conditioning system, characterized in that: The method comprises the following steps: S1. Install a cross-shaped pitot tube on the pipeline to lead out two high and low measuring ports, and connect the two high and low measuring ports to the high and low pressure difference interfaces of the terminal controller respectively; S2. Read the measured pressure difference of the terminal controller through the communication protocol ; At the same time, the pressure difference at the Pitot tube is measured by a handheld differential pressure meter ; The pressure difference measured by the handheld differential pressure meter is monitored in time series, and after its fluctuation is stabilized, the average pressure difference within the preset time is taken as the pressure difference measured by the handheld differential pressure meter. ; S3. Read the pressure difference measured by the handheld differential pressure meter under at least two working conditions. The measured pressure difference with the terminal controller , and finally through the formula: , calculate the pressure difference coefficient k and pressure difference deviation C; S4. Set the calculated pressure difference coefficient k and pressure difference deviation C to the terminal controller to complete the calibration; Under dynamic conditions, the frequency and fluctuation of the air volume of the variable air volume air conditioner are adjusted, and the frequency and fluctuation of the air volume of the terminal controller are monitored to detect the delay of the air volume change. The steps include: Z1. By adjusting the air volume input frequency of the variable air volume air conditioner , simulating periodic fluctuations; And by setting multiple input frequencies , observe the response of the variable air volume air conditioning system at different frequencies; Z2. Real-time monitoring of the pressure difference changes of the terminal device, including: The pressure difference time series is collected by a handheld pressure difference meter to record the pressure difference changes at the measuring pitot tube in the pipeline. ; Z3. Record the air volume through the terminal controller ; Z4. Calculate the delay time of the pressure difference change relative to the change of the air intake volume based on the changes of the air intake volume and the pressure difference , ; In the formula, is the phase difference of the change of the air volume outflow relative to the air volume inflow; According to the changes in air intake and air output, calculate the delay time of the change in air output relative to the change in air intake , ; In the formula, is the phase difference of the change of the air volume outflow relative to the air volume inflow; Finally, the system delay time is obtained by the response delay from air intake to pressure difference and the response delay from air intake to air outlet. The formula is: .

2. The on-site calibration method of a variable air volume air conditioning system terminal device according to claim 1, characterized in that: In step S3, the measured pressure difference through the terminal controller The air volume is calculated using the formula: ,and ; Where S is the cross-sectional area of ​​the duct, is the air density, is the measured pressure difference of the terminal controller, and k is the pressure difference coefficient.

3. The on-site calibration method of a variable air volume air conditioning system terminal device according to claim 2, characterized in that: The method for obtaining the mean value of the differential pressure of the handheld differential pressure meter comprises the following steps: A1. Measure and continuously record differential pressure data using a handheld differential pressure meter , and determine the recording time interval and the total monitoring time T; A2. Pressure difference data Conduct time series monitoring; From time Start by collecting pressure difference data at N consecutive time points , and recorded as a time series: ; A3. Calculate the fluctuation range and change rate of the time series, including: Compute the mean of a time series: , where is the mean value of the time series, The pressure difference data measured by the handheld pressure difference meter at the i-th time point; The formula for calculating the fluctuation range is: , where R is the fluctuation range of the time series, is the maximum value of the pressure difference data in the time series, is the minimum value of the pressure difference data in the time series; The rate of change of the time series is calculated by calculating the standard deviation of the time series. The formula is: ; Preset the allowed fluctuation range threshold and the preset standard deviation threshold ; When the fluctuation range of the time series R ≤ the fluctuation range threshold , and the time series standard deviation ≤Standard Deviation Threshold When determining the pressure difference data measured by the handheld differential pressure meter Satisfy stability and the pressure difference data at subsequent times Mark as steady-state pressure difference and record the stable time point ; A4. At the stable time point Some time later Calculate the mean value of the steady-state pressure difference using the formula: , where is the mean value of the steady-state pressure difference, Z is the number of sampling points corresponding to the time M, The differential pressure data is marked as steady-state differential pressure.

4. The on-site calibration method of a terminal device of a variable air volume air conditioning system according to claim 3, characterized in that: Repeat steps A1-A4 to calculate the measured pressure difference of the terminal controller marked as steady-state pressure difference ; The measured differential pressure of the terminal controller is marked as the steady-state differential pressure The handheld differential pressure meter is marked as the mean pressure difference of the steady-state differential pressure. Applied to the calculation in step S3, namely: The air volume calculation formula is: ; The calculation formula for the pressure difference coefficient k and the pressure difference deviation C is: .

5. The on-site calibration method of a variable air volume air conditioning system terminal device according to claim 1, characterized in that: The terminal controller establishes a dynamic correction model based on the system delay time: ; In the formula, is the dynamic pressure difference coefficient, k is the pressure difference coefficient calculated in step S4, and α is the delay correction coefficient.

6. The on-site calibration method of a terminal device of a variable air volume air conditioning system according to claim 5, characterized in that: Under dynamic conditions, the air volume calculation formula is corrected to: ; And under dynamic conditions, if the pressure difference deviation C deviates from the calibration value, the formula is: Make corrections; where is the dynamic pressure difference deviation, and β is the deviation correction coefficient.

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